The present invention relates generally to sulfurpentafluoride compounds having a substituted silyl group wherein at least one of the substituents is hindered and methods for making and using same. This invention also relates to the use of these compounds, for example, as precursors to liquid crystal components, surfactants, bioactive compounds in agrochemical and pharmaceutical compositions, or in polymers.
The development of synthetic methodologies for the introduction of sulfurpentafluoride or pentafluorosulfuranyl groups (xe2x80x9cSF5xe2x80x9d) into organic compounds has been pursued with a considerable degree of interest by several research groups. It is believed that the SF5 group may impart unique properties to these organic compounds that include, inter alia, low surface energy, high chemical resistance, high thermal stability, high electronegativity, hydrophobicity, and high dielectric constant. For instance, the high electronegativity value of the SF5 group, 3.62 on the Pauling scale, and greater electron withdrawing ability may make it an attractive alternative for the trifluoromethyl group (xe2x80x9cCF3xe2x80x9d) found in many commercial products.
Organic compositions containing SF5 have been used in a variety of applications. For example, EP 444822, issued to Hansen and Savu describes pentafluorosulfuranyl fluoroaliphatic compositions that are used as surfactants. The reference, Kovacina et. al., Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 2, 170, describes SF5-containing polymers that are prepared from mono and bis (pentafluorosulfur)-substituted diacetylenes. These polymers are soluble in fluorinated solvents and are not shock sensitive in comparison to the hydrocarbon analog. U.S. Pat. No. 6,136,838 describes sulfur pentafluorophenyl pyrazoles that are used for the control of ecoparasitic infections. Lastly, DE 19748109 issued to Kirsch et. al (xe2x80x9cKirschxe2x80x9d) describes the preparation of several sulfurpentafluoride derivatives which are used to prepare liquid-crystal media.
Ethynylsulfur pentafluoride (SF5CCH) has been oftentimes used as a synthetic intermediate or delivery vehicle for the introduction of the SF5-moiety into complex organic compounds. Current methods to isolate SF5CCH have only been achieved in small scale, multi-step reactions. See, e.g., Hoover and Coffman, J. Am. Chem. Soc. 1964, 29, 3567(xe2x80x9cHooverxe2x80x9d); Canich et. al. Inorg. Chem. 1985, 24, 3668 (xe2x80x9cCanichxe2x80x9d). Both Hoover and Canich describe four-step reactions to prepare SF5CCH from acetylene and either sulfur chloride or sulfur bromide pentafluoride. The yields from these reactions ranged from 9 to 19%. Canich also describes a method of isolating ethynylsulfur pentafluoride via dehydrobromination of SF5CHxe2x95x90CHBr with a 49% yield. In the first step, SF5CHxe2x95x90CHBr was prepared in 80% yield from the reaction of acetylene and SF5Br which took approximately 4 days and was conducted at 57xc2x0 C. Based upon this, the expected yield of ethynylsulfur pentafluoride after completion of the second step would be approximately 39%. Dehydrohalogenation of the acetylene SF5CHxe2x95x90CHCl resulted in product yields of only 1-2% of the desired alkyne. The relatively low yields, inefficiency, and long cycle times may make these processes impractical for large-scale industrial applications. Moreover, the reaction of acetylene with SF5Br or SF5Cl at high temperatures may be explosive.
Ethynylsulfur pentafluoride may also be obtained by the desilylation of its trialkylsilyl derivative. See Wessel et. al. Chem. Ber. 1986, 119, 45 (xe2x80x9cWesselxe2x80x9d). Like the aforementioned methods to isolate SF5CCH, the trimethylsilyl derivative of ethynylsulfur pentafluoride is impractical to produce on an industrial scale. The trimethylsilyl derivative of ethynylsulfur pentafluoride prepared as described in Wessel was obtained with only a 12% isolated yield.
Accordingly, there is a need in the art to provide novel compounds that deliver the SF5 group into an organic compound. Depending upon the application, there may be a further need to provide novel compounds that deliver a substituted silyl group to an organic compound. There is also a need in the art for safe industrial processes to make SF5 synthetic intermediates at greater yields, less cycle time, lower process temperatures, less volatility, and in a single reaction vessel. Due to the difficulties in the art in isolating the trimethylsilyl derivative of ethynlsulfur pentafluoride, it is thus surprising and unexpected to produce novel substituted-silyl sulfurpentafluoride compounds at relatively high yields when at least one of the substituents of the silyl group is hindered.
All references cited herein are incorporated herein by reference in their entirety.
The present invention is directed, in part, to sulfurpentafluoride-containing compounds having a substituted silyl group. Specifically, in one embodiment of the present invention, there is provided a compound of the formula: 
wherein the substitutents R, Rxe2x80x2, and Rxe2x80x3 may be an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substitutents is hindered. In a preferred embodiment, R, Rxe2x80x2, and Rxe2x80x3 comprise isopropyl. In another preferred embodiment, R and xe2x80x2 comprise methyl and Rxe2x80x3 comprises t-butyl.
In a further embodiment of the present invention, there is provided a compound comprising a sulfurpentafluoride group and a substituted silyl group that is bonded to the sulfurpentafluoride group by a Cxe2x80x94C triple bond. The substituted silyl group has substituents selected from the group consisting of an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substituents is hindered. In another embodiment of the present invention, there are provided liquid crystal precursors that comprise the compounds of the present invention.
In yet a further embodiment of the present invention, there is disclosed a method for making a substituted silyl sulfurpentafluoride ethyne compound wherein the substituents on the silyl group are selected from the group consisting of an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substituents is hindered. The method comprises the steps of: combining a substituted silyl acetylenic compound with a SF5-containing halide under conditions sufficient to provide an intermediate product and exposing the intermediate product to a base under conditions sufficient to provide the ethyne compound. In certain preferred embodiments, the combining step is conducted in the presence of a solvent.
These and other aspects of the invention will become apparent from the following detailed description.
The present invention is directed to sulfurpentafluoride-containing compounds having a substituted silyl group and methods for making and using same. The compounds of the present invention are suitable for use by themselves or in delivering sulfurpentafluoride groups and/or silyl groups to a variety of organic compositions. In addition, the methods of the present invention produce sulfurpentafluoride-containing compounds at production yields unattainable heretofore.
The compounds of the present invention comprise at least one sulfurpentafluoride grouping that is joined to a substituted silyl group via an unsaturated carbon bond. Preferably, the compound is an ethyne compound wherein the sulfurpentafluoride group is joined to the substituted silyl group via a Cxe2x80x94C triple bond. At least one of the substituents on the silicon atom is hindered. The term xe2x80x9chinderedxe2x80x9d or xe2x80x9csterically hinderedxe2x80x9d as used herein relates to radical groups that impede or retard a given reaction with another molecule by virtue of its size. Some non-limiting examples of hindered alkyl groups include large primary (1o) alkyl groups such as octadecyl or nonadecyl; secondary (2o) alkyl groups such as isopropyl, isobutyl, or isopentyl; or tertiary (3o) alkyl groups such as tert-butyl (xe2x80x9ct-butylxe2x80x9d) or tert-pentyl (xe2x80x9ct-pentylxe2x80x9d).
In certain preferred embodiments, the sulfurpentafluoride-containing compound has the following formula: 
The silyl group within the compound is substituted, preferably trisubstituted, with radicals R, Rxe2x80x2, and Rxe2x80x3. Substituents R, Rxe2x80x2 and Rxe2x80x3 represent one or more substituents, like or different, that may comprise an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, or combinations thereof. At least one of the substituents on the silicon atom is hindered.
As mentioned previously, subsitutents R, Rxe2x80x2, and Rxe2x80x3 may be an alkyl or substituted alkyl group. The term xe2x80x9calkylxe2x80x9d as used herein includes straight chain, branched, or cyclic alkyl groups; preferably containing from 1 to 20 carbon atoms, or more preferably from 1 to 10 carbon atoms. This applies also to alkyl moieties contained in other groups such as haloalkyl, alkaryl, or aralkyl. The term xe2x80x9csubstituted alkylxe2x80x9d applies to alkyl moieties that have substituents that include heteroatoms such as O, N, S, or halogen atoms; OCH3; OR (Rxe2x95x90H, alkyl C1-10, or aryl C6-10); alkyl C1-10 or aryl C6-10; NO2; SO3R (Rxe2x95x90H, alkyl C1-10, or aryl C6-10); or NR2 (Rxe2x95x90H, alkyl C1-10 or aryl C6-10). The term xe2x80x9chalogenxe2x80x9d as used herein includes fluorine, chlorine, bromine, and iodine. In certain preferred embodiments, R, Rxe2x80x2, Rxe2x80x3 are individually 2o or 3o alkyl groups or combinations of 1o, 2o, and 3o alkyl groups with at least one 2o or 3o alkyl. Preferred substituents are when R, Rxe2x80x2, and Rxe2x80x3 are each isopropyl or when R and Rxe2x80x2 are CH3 and Rxe2x80x3 are t-butyl.
The substitutents R, Rxe2x80x2, Rxe2x80x3 can also be an aryl or substituted aryl group. The term xe2x80x9carylxe2x80x9d as used herein six to twelve member carbon rings having aromatic character. The term xe2x80x9csubstituted arylxe2x80x9d as used herein includes aryl rings having subsitutents that include heteroatoms such as O, N, S, or halogen atoms; OCH3; OR (Rxe2x95x90H, alkyl C1-10, or aryl C6-10); alkyl C1-10 or aryl C6-10; NO2; SO3R (Rxe2x95x90H, alkyl C1-10, or aryl C6-10); or NR2 Rxe2x95x90H, alkyl C1-10 or aryl C6-10).
The compounds of the present invention are preferably prepared in a two-step process, as shown in Steps I and II below. This process may be performed in a single reaction vessel. This two-step process produced the desired product in excellent yield, from about 80% to about 99% of the theoretical yield, when at least one of the substituents on the silicon atom is hindered. By contrast, when the substituent on the silicon atom is relatively unhindered such as, for example, CH3, the product is obtained in lower yield due to the cleavage of the silyl group during the second or elimination step. In Step I, a substituted silyl acetylene, preferably a trisubstituted silyl acetylene wherein at least one of the substituents is hindered, is reacted with a SF5-containing halide to form a vinylic pentafluorosulfuranyl intermediate. The substituents on the silicon atom can be any of the substituents disclosed herein. In Step II, the hydrogen and halide within the vinylic pentafluorosulfuranyl intermediate is eliminated in the presence of a base to form the final product. 
The first step of the process involves the reaction of a substituted silyl acetylenic compound with a SF5-containing halide such as SF5Br or SF5Cl to produce an intermediate product which is an alkene bearing a halide atom and an xe2x80x94SF5 group on adjacent carbons. At least one of the substituents on the silicon atom is hindered. This reaction may occur in the presence of a solvent. In embodiments where a solvent is used, the solvent selected will not react with the SF5-containing halide or the intermediate product. Suitable solvents include, but are not limited to, hydrocarbons (e. g. pentane or hexane); halocarbons (e. g. Freon 113); ethers (e. g. ethylether (Et2O) or tetrahydrofuran (xe2x80x9cTHFxe2x80x9d)); nitrites (e. g. CH3CN); or aromatic compounds (e.g. benzotrifluoride). The reaction temperature may range from xe2x88x9278xc2x0 C. to the boiling point of the solvent. The reaction time for the first step may range from about 0 hours or instantaneous to about 8 hours, preferably from about 0.1 to about 6 hours, or more preferably from about 0.5 to about 4 hours. The anticipated yield of the intermediate product ranges from about 80% to about 99% of the theoretical yield.
In the second or elimination step, the vinylic pentafluorosulfuranyl intermediate product of the first step is combined with a base to form the substituted silyl sulfurpentafluoride ethyne compound. The term xe2x80x9cbasexe2x80x9d as used herein is any compound capable of exchanging negatively charged ions such as, but not limited to, hydroxide, halide, alkoxide, amide, organolithium, or organomagnesium ions. Examples of suitable bases include alkali metal and alkaline earth metal hydroxides. In some embodiments, the second step may be conducted in the presence of a solvent. Solvents that may be used in the second step include any of the solvents used in the first step as well as water. The temperature for the second step may range from xe2x88x9278xc2x0 C. to the boiling point of the solvent. The reaction time for the second step may range from about 0 to about 24 hours or preferably from about 1 to about 16 hours. The anticipated yield of the ethyne compound ranges from about 80% to about 99% of the theoretical yield. The molecular weight of the ethyne compound ranges from about 225 to about 800 or more preferably about 225 to about 400. The final product may be purified by standard procedures such as distillation or chromatography.
The compounds of the present invention may be used as synthetic intermediates or starting reagents in any organic composition in which the organic composition requires the introduction of SF5 and/or silyl groups into the composition. The compounds may be useful as a starting reagent for a number of derivatives that include, but are not limited to, saturated ethers, vinyl ethers, pyrazoles, cyclic alkenes, and SF5-containing alkenes and alkynes. These compounds may also be used as an attractive alternative to reagents containing the CF3 group. In this connection, the compounds of the present invention can be used as precursors within liquid crystal compositions such as those disclosed in U.S. Pat. Nos. 5,728,319 and 5,792,386 in place of those derivatives containing the CF3 group. The substituted silyl group may be extracted during the preparation of the liquid crystal composition. The compounds of the present invention may also be used within surfactant compositions such as those described, for example, in EP 444822. Further uses for the compounds of the present invention include precursors or reagents within pharmaceutical compositions such as the compositions described, for example, in U.S. Pat. No. 6,136,838.
The compounds of the present invention can be incorporated within polymers such as polyacrylates, polyesters, polyurethanes, polyamides, and polyvinyl ethers made by conventional step-growth, chain-growth, or graft polymerization techniques or processes. In some instances, the ethyleneically unsaturated compounds of the present invention can be homopolymerized to make homopolymers or copolymerized with copolymerizable monomers to make random, alternating, block, or graft polymers. In these applications, for example, the silyl group of the compound may either be removed from the polymer composition prior to completion or may remain within the polymer to enhance certain properties of the polymer such as, for example, adhesive strength.
The invention will be illustrated in more detail with reference to the following examples, but it should be understood that the present invention is not deemed to be limited thereto. The gas chromatograph (xe2x80x9cGCxe2x80x9d) analyses were carried out on a 30M RTX-5 column. The G.C.M.S. Spectra for the examples were performed on a Hewlett Packard 5890 Series 11 G.C. and 5972 series mass selective detector with a HP-5MS. The nuclear NMR analyses for the examples were obtained on a Bruker CP-300FT spectrometer operating at 282.4 MHz (19F), 300.13 MHz (1H). Chemical shifts were referenced to neat in CFCl3(19F) and CH Cl3 (1H). The results for the examples are presented in Table I.